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如图,半径R=1m的光滑半圆轨道AC与高8R的粗糙斜面轨道BD放在同一竖直平面内,BD部分水平长度为6R.两轨道之间由一条光滑水平轨道相连,水平轨道与斜轨道间有一段圆弧过渡.在水平轨道上,轻质弹簧被a、b两小球挤压(不连接),处于静止状态.同时释放两个小球,a球恰好能通过半圆轨道最高点A.已知a球质量为m1=2kg,b球质量为m2=1kg,小球b与斜面间动摩擦因素为μ=
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3
,重力力加速度为g=10m/s2.(sin37°=0.6,cos37°=0.8)求:
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    More and more comment(评论) sections are being shut down online.

    Autumn Phillips had had enough. On August 19, the executive editor of the Quad-City Times in Iowa, and Illinois, US visited her website, qutimes. com, and saw a story about a man who had been shot to death. When she got to the readers' comments section at the end, she was shocked by what she saw. Below the story was a growing string of comments—a racist remark about democratic( 民主的) voters, a negative comment about police...So Phillips decided to do something she had been thinking about for a long time: she shut down the comment section.

    Phillips was not alone in making such a move. Last week, NPR announced it too was closing its online comments section. The decisions don't mean that the news outlets are no longer interested in what their audiences are thinking. Both stressed their eagerness to hear from readers and listeners on social networks. But both agreed that comments had deviated from their original intention. And so they had.

    In the early days of digital journalism, comments were seen as a key part of the new media, a wonderful opportunity for strengthening the dialogue between news producers and their audiences. It was a welcome change, given that for long many news organizations were far too separated from their readers. Much more back and forth conversation seemed like healthy and welcome evolutions. Sadly, that's not the way things turned out. Rather than a place for exchanging ideas, comments sections became the home of ugly name-calling, racism and anti-women language. Besides their poisonous quality, comments seem out of place today.

    “Since we made the announcement, I've received an outpouring of responses from our readers,”she says. “I've heard from parents whose children were hurt by our online comments. I've heard from people who said they wouldn't send in letters to the editor because they were attacked so fiercely by comments, and it wasn't worth it.”